"On the day that the family were due to travel to Bangladesh (9 April), one of the members of the party was stopped at Heathrow Airport and was subject to a schedule 7 examination. At the time the schedule 7 was taking place, a search was carried out at their home address in Spencer Road, Luton.

There was no information, either through the schedule 7 or search, which suggested that any of the family were intending to travel to Syria, so they were allowed to travel the following day without any police intervention. While the suggestion is that the party’s current location is in Syria, this remains uncorroborated and our enquiries are continuing.

We are not prepared to comment any further due to the fact there is an on-going investigation."

The party had initially travelled to Bangladesh from Heathrow via Istanbul on 10 April.

They flew back to Istanbul on 11 May and were due to fly back to Heathrow on 14 May. However they failed to return and were reported missing by a relative in Luton on 17 May.

Anyone with any information about the 12 is urged to call police on 101.